Control device, optical system, lithography installation and method

Abstract

A control device for controlling and measuring an actuator for actuating an optical element of an optical system, comprises a voltage measuring unit, a current measuring unit, a first matched filter unit and a second matched filter unit. A method for controlling and measuring an actuator for actuating an optical element of an optical system comprises: providing a measurement voltage; providing a measurement current; estimating, via a first matched filter unit, a voltage amplitude and an associated phase of a measurement signal component; estimating, via a second matched filter unit, a current amplitude and an associated phase of the measurement signal component; and calculating an impedance of an actuator based on the estimated voltage amplitude, the estimated associated phase, the estimated current amplitude and the estimated associated phase.

What is claimed is: 
     
         1 . A control device, comprising:
 a voltage measuring unit configured to provide a measurement voltage indicative of a time-dependent voltage of an actuator controlled via an excitation signal based on a specific model, the excitation signal comprising a sinusoidal measurement signal component configured to measure an impedance of the actuator;   a current measuring unit configured to provide a measurement current indicative of a time-dependent current of the actuator controlled via the excitation signal;   a first matched filter unit configured to estimate a voltage amplitude and an associated phase of the measurement signal component arising at the actuator based on the measurement voltage provided and the specific model of the excitation signal;   a second matched filter unit configured to estimate a current amplitude and an associated phase of the measurement signal component arising at the actuator based on the measurement current provided and the specific model of the excitation signal; and   a calculation unit configured to calculate the impedance of the actuator based on the estimated voltage amplitude, the estimated associated phase, the estimated current amplitude and the estimated associated phase.   
     
     
         2 . The control device of  claim 1 , wherein the first matched filter unit is configured to use a linear least squares estimate to estimate the voltage amplitude and the associated phase of the measurement signal component arising at the actuator using the measurement voltage provided and the specific model of the excitation signal. 
     
     
         3 . The control device of  claim 2 , wherein the first matched filter unit is configured to carry out the linear least squares estimate based on a Moore-Penrose inverse, the Moore-Penrose inverse comprising coefficients suitable for the compensation of a transfer function of the voltage measuring unit. 
     
     
         4 . The control device of  claim 1 , wherein the second matched filter unit is configured to use a linear least squares estimate to estimate the current amplitude and the associated phase of the measurement signal component arising at the actuator using the measurement current provided and the specific model of the excitation signal. 
     
     
         5 . The control device of  claim 4 , wherein the second matched filter unit is configured to carry out the linear least squares estimate on the basis of a Moore-Penrose inverse, the Moore-Penrose inverse comprising coefficients suitable for the compensation of a transfer function of the current measuring unit. 
     
     
         6 . The control device of  claim 1 , further comprising a signal generator configured to provide the excitation signal. 
     
     
         7 . The control device of  claim 6 , wherein the signal generator is configured to provide the excitation signal so that the excitation signal comprises a control signal component configured to set a specific position of the controlled actuator and the sinusoidal measurement signal component for measuring the impedance of the actuator. 
     
     
         8 . The control device of  claim 7 , wherein the specific model of the excitation signal is determined by the following equation: 
       
         
           
             
               
                 
                   y 
                   ⁡ 
                   ( 
                   t 
                   ) 
                 
                 = 
                 
                   O 
                   + 
                   
                     a 
                     * 
                     
                       sin 
                       ⁡ 
                       ( 
                       
                         
                           2 
                           ⁢ 
                           π 
                           ⁢ 
                           ft 
                         
                         + 
                         φ 
                       
                       ) 
                     
                   
                 
               
               , 
             
           
         
         where y(t) denotes the excitation signal, O denotes the control signal component, a denotes the amplitude, f denotes the frequency, t denotes the time and φ denotes the phase. 
       
     
     
         9 . The control device of  claim 6 , further comprising a control unit coupled to the signal generator and the actuator, wherein the control unit is configured to output to the actuator a time-dependent control voltage configured to control the actuator based on the excitation signal provided by the signal generator. 
     
     
         10 . The control device of  claim 9 , wherein:
 the first matched filter unit is configured to use a linear least squares estimate to estimate the voltage amplitude and the associated phase of the measurement signal component arising at the actuator using the measurement voltage provided and the specific model of the excitation signal;   the second matched filter unit is configured to use a linear least squares estimate to estimate the current amplitude and the associated phase of the measurement signal component arising at the actuator using the measurement current provided and the specific model of the excitation signal;   the control unit comprises a frequency-dependent first transfer function and the control unit is configured thereby to amplify the excitation signal comprising a first frequency range and a second frequency range to form the control voltage for the actuator so that the first frequency range experiences a higher gain vis-à-vis the second frequency range by a specific factor;   the voltage measuring unit is configured to provide the measurement voltage based on a second transfer function that is based on an inverse of the first transfer function;   the current measuring unit is configured to provide the measurement current based on a third transfer function that is based on an inverse of the first transfer function.   
     
     
         11 . The control device of  claim 10 , wherein:
 the first matched filter unit is configured to carry out the linear least squares estimate on the basis of a Moore-Penrose inverse, the Moore-Penrose inverse comprising coefficients suitable for the compensation of the second transfer function of the voltage measuring unit; and   the second matched filter unit is configured to carry out the linear least squares estimate on the basis of a Moore-Penrose inverse, the Moore-Penrose inverse comprising coefficients suitable for the compensation of the third transfer function of the current measuring unit ( 140 ).   
     
     
         12 . The control device of  claim 1 , wherein the specific model of the excitation signal is determined by the following equation: 
       
         
           
             
               
                 
                   y 
                   ⁡ 
                   ( 
                   t 
                   ) 
                 
                 = 
                 
                   a 
                   * 
                   
                     sin 
                     ⁡ 
                     ( 
                     
                       
                         2 
                         ⁢ 
                         π 
                         ⁢ 
                         ft 
                       
                       + 
                       φ 
                     
                     ) 
                   
                 
               
               , 
             
           
         
         where y(t) denotes the excitation signal, a denotes the amplitude, f denotes the frequency, t denotes the time, and φ denotes the phase. 
       
     
     
         13 . The control device of  claim 1 , wherein the signal generator is configured to provide the excitation signal as a broadband excitation signal comprising a plurality of sinusoidal measurement signal components configured to simultaneously measure the actuator at a plurality of different frequencies. 
     
     
         14 . The control device of  claim 1 , wherein the calculation unit is configured to calculate the complex impedance of the actuator based on a phase shift between the phase associated with the voltage amplitude and the phase associated with the current amplitude and a quotient between the voltage amplitude and the current amplitude. 
     
     
         15 . An optical system, comprising:
 an optical element;   an actuator; and   a control device according to  claim 1 ,   wherein the actuator is configured to actuate the optical element.   
     
     
         16 . The optical system of  claim 15 , wherein the optical system is lithography illumination optical unit, or a lithography projection optical unit. 
     
     
         17 . An optical system, comprising:
 a plurality of optical elements;   a plurality of actuators; and   a plurality of control devices according to  claim 1 ,   wherein each actuator has a corresponding control device, and each actuator is configured to actuate a corresponding optical element.   
     
     
         18 . The optical system of  claim 17 , wherein the optical system is lithography illumination optical unit, or a lithography projection optical unit. 
     
     
         19 . An apparatus, comprising:
 a plurality of optical elements;   a plurality of actuators; and   a plurality of control devices according to  claim 1 ,   wherein each actuator has a corresponding control device, each actuator is configured to actuate a corresponding optical element, and the apparatus is a lithography apparatus.   
     
     
         20 . A method of controlling and measuring an actuator configured to actuate an optical element of an optical system, the method comprising:
 providing a measurement voltage indicative of a time-dependent voltage of the actuator controlled via an excitation signal based on a specific model, the excitation signal comprising at least one sinusoidal measurement signal component for measuring the impedance of the actuator;   providing a measurement current indicative of a time-dependent current of the actuator controlled via the excitation signal;   estimating, using a first matched filter unit, a voltage amplitude and an associated phase of the measurement signal component arising at the actuator using the measurement voltage provided and the specific model of the excitation signal;   estimating, using a second matched filter unit, a current amplitude and an associated phase of the measurement signal component arising at the actuator using the measurement current provided and the specific model of the excitation signal; and   calculating the impedance of the actuator on the basis of the estimated voltage amplitude, the estimated associated phase, the estimated current amplitude and the estimated associated phase.